­Kermit the Frog once said, "It's not that easy bein' green." Although he wasn't referring to cars, his observation seems particularly appropriate for the auto industry today: Designing, developing and marketing "green" cars has not been an easy task, which is why gasoline-powered vehicles still rule the road and fossil fuels still account for almost 75 percent of the world's energy consumption. As gasoline prices soar and concern over harmful emission mounts, however, cars that run on alternate fuel sources will become increasingly important. A natural-gas vehicle, or NGV, is the perfect example of such a car -- it's fuel-efficient, environmentally friendly and offers a relatively low cost of ownership.

This article will explain the basic idea of NGVs, look at the unique design challenges involved and examine the advantages and benefits of this technology.

Discovery

Some scholars speculate that people living in the Middle East discovered this property of natural gas between 6000 and 2000 BC when lightning strikes ignited natural gas seeping from the ground. The Chinese burned natural gas as early as 211 BC to dry rock salt found in limestone rock. They also drilled the first known natural gas wells, using bamboo poles and primitive bits, but they were only able to reach depths of 500 feet.